We are attempting to gain insight into the biological and biochemical events that regulate and determine tissue-specific gene expression and the alterations that accompany or are consequent to neoplastic transformation. Three biological systems, each exemplifying differential gene regulation, are under study. Alpha 2u globulin, a protein that had been thought to be synthesized exclusively in the liver, has now been shown also to be made in the submaxillary and lachrymal glands. We have shown that one subset of the alpha 2u gene family is hormonally dependent and expressed in the liver and another subset of these genes is constitutively expressed in the salivary and lachrymal glands. We have cloned and are sequencing several of these genes and corresponding cDNAs. We have inserted several of the cloned hepatic and salivary types of alpha 2u globulin genes into mouse fibroblast cells in culture. Experiments are under way to determine the structure of alpha 2u globulin genes responsible for their hormonal control and tissue-specific expression. Hepatomas contain alpha 2u globulin RNA species, which seem incapable of directing synthesis of alpha 2u globulin. In hopes of gaining insight into how gene expression is altered in neoplastic cells, studies are under way to ascertain from how alpha 2u globulin RNA derived from neoplastic cells differs from its normal counterpart. We have inserted genes derived from tumors, which encode aberrant forms of immunoglobulin, into myeloma and hybridoma cells maintained in vitro. These studies indicate that internal portions of the gene enhance its expression. A series of experiments indicate that, when gene encoding mouse light chain is introduced into cells that do not normally express this gene, then gene expression is suppressed. The nature of this tissue-specific control is under investigation. Thyroid hormone has been shown to act on nontransformed liver cells to elevate levels of several enzymes but does not do so when added to cultures of transformed hepatocytes. The biochemical events underlying the synthesis, assembly, and integration of ATPase into the cell membrane is under active exploration. Assembly of two of the subunits after their cell-free biosynthesis has been observed. (V)